COVID-19 Data Breakdown: New and Ongoing Outbreaks

Since August, the State of Michigan collected in-depth data from local health departments about the settings of COVID-19 outbreaks on a weekly basis. The outbreak data can be used to understand where mitigation measures could be more effective in combating community spread. The state reports two different outbreak types: new outbreaks, which were just identified in the previous week, and ongoing outbreaks, where at least one new case associated with a particular outbreak was reported to the local health department in the last two weeks. The current report for each Emergency Preparedness Region, as well as the statewide totals, can be found on the state’s covid website, along with an excel spreadsheet with historical data of varying levels of detail. The most recent classifications of outbreak settings began on August 27, 2020, so that is when we start analyzing outbreak data.

Some settings, such as churches and restaurants might be more difficult to contact trace than others, like long term care facilities. So it’s important to remember that disparities between settings might be impacted by other factors instead of a concrete measure of the difference in risk of those settings.

New outbreaks peaked the week of November 23, right after the Michigan Department of Health and Human Services (MDHHS) implemented the “Pause to Save Lives” initiative. While new outbreaks haven’t declined to the levels of late summer, there is a clear and consistent downward trend since Thanksgiving, and notably less than 150 new outbreaks statewide for most of 2021 (January 28, 2021 saw 164 new outbreaks). 

The ongoing outbreaks can also give us an idea of the magnitude of an outbreak. A new outbreak moves to ongoing the week after it is reported and stays until there have been no new reported cases associated with the outbreak for 14 days, the standard quarantine period. Therefore, a higher number of ongoing outbreaks means that people are continuing to infect others and more people are getting sick from a single situation overall. Ongoing outbreaks peaked on December 10, 2020 and have steadily declined since then. This is probably due to a combination of the statewide limitations placed on group gatherings and indoor dining, vaccination efforts (the first vaccination distribution is recorded onDecember 14th), and holiday season ending. As new venues continue to open up, particularly high schools and restaurants, keeping an eye on these outbreaks will be important for managing the state’s restrictions.

Outbreak Settings

Since August 27, 2020, local public health departments have reported 3,838 new outbreaks statewide. Outbreaks are reported broken out by detailed settings on the state’s website

Combining all the reported new outbreaks since August 27, 2020, we can see where outbreaks are more likely to be reported. For this analysis, we combined some of the settings to provide a more comprehensive understanding of the situation. For example, there are four categories related to bars and restaurants that are reported in the table below as a single number.

Long term care facilities account for nearly 25% of all new outbreaks statewide since August 2020. This highlights the particular risk that COVID-19 presents to older nursing home residents, but also other congregate care facilities. K-12 Schools and manufacturing/construction account for the next quarter of outbreaks. While some types of settings, like restaurants and religious services, are comparably low, it’s important to remember that this data is only representative of what local health departments can effectively contact trace. Prior to November, restaurants were not required to collect names of patrons and were shut down for nearly three months of this data collection period. Even now that names and phone numbers are required for dining-in, effective contact tracing requires Michiganders to cooperate by providing accurate information. 

Since there are many factors impacting outbreaks, we’re going to look more closely at long term care facilities, education-related settings, and bars and restaurants to better understand how policies, seasons, and vaccinations might be impacting these outbreak numbers. For the following charts, new and ongoing outbreaks are combined, since an outbreak continuing for multiple weeks indicates long-term challenges for these settings to help mitigate. 

Long Term Care Facilities

Outbreaks in long term care facilities have remained one of the leading settings for outbreaks in the state, which peaked in the week of December 30th. The dangers of COVID-19 to elderly populations is well-documented, and congregate living quarters are a prime location for outbreaks due to a variety of shared facilities. While long term care residents account for 4.1% of the state’s total confirmed cases, 36% of coronavirus-related deaths were long term care residents. The state has documented more detailed information about long term care cases, since there is such a large proportion of outbreaks in the state. This data helps give a better understanding of the size of outbreaks in long term care facilities. Looking at the data reported for February 1, 2021, new case reports at individual facilities range from 1-29, with most new case reports being in single digits.

While outbreaks are declining overall, the decline in long term care facilities over the past two months is particularly noteworthy because these facilities have borne an outsized burden of outbreaks, cases, and deaths. This downward trend in long term care facility outbreaks could be partially attributed to the impact of vaccinations limiting spread since vaccinations began for residents on December 28th.

Education-Related Settings

Since August 27, there have been three education-related settings reported on: K-12 schools (including before and after school care), colleges and universities, and childcare and youth programs (including sports programs, daycares, and other extracurricular activities). K-12 Schools are the second largest contributor to overall new outbreaks in the state. Similarly to long term care facilities, education settings generally have a more formalized idea of where people interacted, which can make contact tracing much easier. The nature of school settings also means that sometimes social distancing is not possible due to lab work, classroom sizes, and more.

School-related outbreaks (universities and K-12) are reported by the state in more detail, which helps further understanding of outbreak sizes and the impact these outbreaks have on statewide numbers. An outbreak is defined as 2 or more cases being tied to a single setting. As of February 15, 2021, most school-related outbreaks have less than 10 cases involved. However, there is a tendency for high schools and universities to have larger outbreaks. This additional detail of outbreak size is not provided for childcare centers. Unlike long term care facilities, school data is not reported at the aggregate level, so each week data is refreshed and we cannot estimate how many of Michigan’s cases are due to school-related cases at this time.

School closures for the winter holidays contributed to the significant decline in December and January. The Pause to Save Lives initiative also closed high schools across the state in late November and some school districts opted to not return after Thanksgiving to mitigate potential holiday party-related spread in their schools. These two actions probably combined to start the overall K-12 decline in outbreaks at the beginning of December, prior to the winter holidays starting.

Over the holidays, there was an increase in daycare-related cases, peaking through late November and early December at over 200 outbreaks a week. The lack of a spike after Christmas may be impacted by a variety of things, including daycare closures from Christmas to New Years, the overall impact of the statewide mandate, and the beginning of vaccine rollouts in the community.

Restaurants and Bars

Bars and restaurant data is reported separately at the state level, further disaggregated by patrons and employees for both settings. This chart shows all four report categories, new and ongoing, over time. While altogether these categories account for 5.3% of statewide outbreaks from the end of August to mid February, it’s important to remember that bars and restaurants are fairly unique settings compared to other locations with higher rates of outbreaks since patrons are not identified like individuals are in a care facility, workplace, or education setting. Indoor dining was also completely shut down for nearly half of this time period. Unlike long term care facilities, restaurants and bars have high rates of change in patrons over time, which can change the scale of an outbreak related to this setting. However, the turnover also means that spread can happen quickly, like the Harper’s Bar outbreak over the summer with nearly 200 cases tied to an outbreak in a Lansing-area bar.

Outbreaks related to bars and restaurants peaked at the end of November, as MDHHS was implementing the restaurant shut down. Over the next two months, we see those outbreaks declining, and since there were no indoor dining patrons in December and January, the vast majority of these outbreaks were employee-related. Since indoor dining resumed on February 1st, it is still too early to see the impact of the reopening on outbreaks related to bars and restaurants because of the incubation period of coronavirus, outbreak investigation process, and reporting delays.

The state provides a download of historical data over time at the bottom of the current outbreak data table.  In order to conduct this analysis, we created a single dataset that you can use for future analysis. The data in our spreadsheet ends the week of February 11, 2021, so additional data would need to be cleaned and imported from the state’s most recent dataset if further analysis is to be completed.

If you ever have any questions about data related to COVID-19 or its impact on the Metro Detroit region, please AskD3 or visit our COVID-19 Portal.